You can actually see who makes the bids on players. Also take into consideration there are a lot of guilds with alliances that don't make it public knowledge who help each other out upping bids. I know I've helped friends get the max out of their players, sometimes it works, other times it backfires.
Is there automated bot bidding in the Auction Houses?
Likewise, there are guilds that won't bid against each other which would explain theirs going for a lot and yours going for less. It's far more organic than a bot or as you suspect, since you bring up source code, manipulation on an unethical level by programmers. A lot of people swear on here that the programmers could ruin a wet dream yet at the same time they are able to put together complex algorithms to screw over live players? I suspect their ability is somewhere between those two extremes